How Many Folds is Too Many

Hi Folks,

I am presently designing a 10 inch back loaded horn for bass guitar use. The outside dimensions are somewhat fixed by the amplifier that needs to sit on top, and the size of my car.

The current iteration of the design, which is simulating nicely in Hornresp has four 180 degree bends and two 90 degree bends.

What problems might I find with such a folding (if any), and are their ways to mitigate them? If the only consequence is the horn signing off a little lower than it would if it were a straight horn, that is not undesirable at all.

Where should reflectors be placed, ideally?


Screenshot 2023-10-03 193914.png
 
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Hello laxandredeyed,

You have a lot of different bass boxes, you could build a museum :)

For bass, they say under 500Hz, folding isn't a problem, it will just make your box heavier due to added panels. Above 500Hz warning rises and it's better to avoid folding but 1 or 2 folds you can round corner to avoid parallel walls and reflections. Probably it's not that black and white value and a grey area may exists. But considering back loaded horn it will for sure have a lot of cancellations and probably the big dip will be bellow 500Hz anyway, see attachment.


 

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frugal-phile™
Joined 2001
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Where should reflectors be placed, ideally?

Every fold adds a low pass filter which helps remove HF you do not want coming out the horn mouth. Reflectors in a back horn ar emost often counter-productive.

The LFs will not see the folds. To do bass a horn needs to be BIG. If not it becomes. “TL/quarterwave” enclosure.

Note that LORDSANSUI’s first video does not show a horn but a badly designed TL.

dave
 
I am strugging to make any sense of your speaker drawing. There seems to be no connection from the back chamber to the horn path & the horn path seems to start with a crossection that is close to zero, as might be found in a offset driver horn, or a tapped horn. Posting your Hornresp input screen might help in understanding what you are trying to acheive.
Most reflectors are unecessary and only waste speaker volume.
A back loaded horn seems a poor choice for a Bass Guitar as the speaker may have frequencies that it will be poor at reproducing - Which would be counterproductive when reproducing the rich harmonic content of a Bass Guitar.
 
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@Xoc1 The start of the horn is shown here. It wasn't clear in the previous pic, which was quick and dirty to show the folds


inlet.png




Here's the Hornresp input screen. The aim is to squeeze the most performance I can from a 10 inch driver I have on hand, without exceeding the size of a 1x15 cab I have.

inputscreen_stepped.png


Response


output_step.png


The null at 250hz is badly positioned for bass guitar, which is part of the reason I was asking about folds.. If the higher frequencies are sufficiently attenuated at this point, it might not be a problem.


The null can be removed by tapering the final segment, at the expense of some lower frequency output

input_taper.png


output_taper_grey_stepped.png


This cabinet if/when built will be crossed over to a midrange driver at ~400hz and powered by a plate amplifier with 31 fully parametric EQs. I fully expect that I will need to use a fair bit of that EQ to get things sounding smooth

Here's the spec sheet for the driver. Not your average 10 given its 9mm xmax and 700w thermal power handling. It's very low vas and Qes limit it's applications .

driver specs.png



Advice is very much appreciated!
 
@GM its hard to know what this driver was designed for, but with the very large motor for a pro sound 10 and a high xmax, I could only conclude the answer is horn loaded subwoofers.

I initially tried to get the compression ratio down, but I could not get 60hz performance (second harmonic of a B string on a bass) without bringing the throat area right down.
 
Thanks for the links and advice.

In order to have wider bandwidth and considering you are open to have horn, it means = big, It might be much better for you to build a Front Loaded Horn with sealed chamber or vented one instead of Rear Loaded Horn. There are many that advocates that nothing sound as good as horn loaded boxes, other that don't like it at all. But honestly, if space isn't a problem sealed front loaded horn might be very pleasant and detailed sounded.

If you consider sealed version It can be very big as the SuperBassHorn or small as SmallHorn, etc
If you consider vented ones, there are also many different layouts such as SHINSON, WLX, WMX, Altec817, etc

Adding vent improve low end extension at the price of increasing group delay and lower frequencies. You may need many interactions to proper fine tune the best trade off or just go for sealed version.

To have wider bandwidth, avoid offset horn, If you consider taking offset horn, like Shinson or any other that has offset horn, it can be fixed adding panel and throat adapter, this will remove the offset effect and throat adapter helps to improve upper frequencies range. While for Subwoofer there are things that you don't care, for a wide range, like guitar box, you really need to pay more attention to select a box design candidate and also details while building.
 
Spec wise it's designed for a prosound midbass BR such as Vb = Vas/1.44, Fb = 1.56x Fs to max out its performance without exceeding Xmax. For compression horn loading its diaphragm/suspension would be 'bullet proofed' to handle it and even then limited to ~3:1 @ high power.
 
@GM "lowercomp" is a 3:1 I am tinkering with, while "700_taper" is the design you commented as having too high a compression ratio.

Interestingly, the lowercomp design still compares well with a 4x10 bass reflex cabinet I have at maximum spl

BLH_BR COMP.jpg
 

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Looking at the sims and your drawing the back chamber seems small in the sims at 2 litres in lowercomp & 3 litres in higher comp - but if I scale the drawing overall size as measured in pixels against a total volume of 135 litres & then measure the chamber size, I get a calculated volume of approx 14 litres for the chamber. which when added to the sim gives a much changed response!